Temperature-Dependent Spontaneous Resolution of a Tetrahedral Chiral-at-Nickel(II) Complex under Supramolecular Control.

Although stereochemical control of carbon centers is a well-established technique in modern synthetic chemistry, that of tetrahedral metal complexes with a stereogenic metal center remains difficult due to the dynamic nature of their coordination bonds. Here we report the synthesis of a tetrahedral d 8 high-spin chiral-at-nickel(II) complex composed exclusively of achiral ligands and the supramolecular control of its temperature-dependent spontaneous resolution in crystals. Under certain conditions, complex molecules with the same absolute configuration of the nickel(II) center grow into conglomerate crystals with a helically arranged structure due to intermolecular hydrogen bonding. This process is highly spontaneous, does not require any chiral sources, and is closely related to the origin of homochirality in biological systems. The obtained enantiopure nickel(II) complex will be a new type of redox-active chiral source for asymmetric synthetic chemistry.